In subsea hydrocarbon extraction facilities, there is a requirement to limit the amount of force exerted on subsea structures. In particular, where connectors, such as flying leads (i.e. subsea jumper systems providing interconnections within a subsea development), are connected to multiple quick connection (MQC) plates on a subsea structure there is the possibility that a jumper containing the flying lead may become snagged, for example, by anchors or trawl boards, and a tensile force exerted on the jumper that is transmitted to, and causes damage to, the subsea structure. It is therefore prudent to install a sacrificial breakaway system which can limit the amount of force that may be exerted on a subsea structure through a jumper.
Such systems are known. These comprise breakaway mechanisms that disconnect all of the flying leads in the jumper simultaneously. An example would be a mechanism comprising a pair of MQC plates populated with male and female connectors and held to one another using a hydraulic release unit. If a jumper connected to one of the MQC plates is pulled with a force exceeding a predetermined limit, the hydraulic release unit will release the two MQC plates. However, all the connectors between the MQC plates will be disconnected simultaneously.
This type of known system has problems, e.g. it could cause problems in subsea hydrocarbon extraction facilities as unless a sequential shutdown order of components in the facility is followed, damage can be caused to well components (e.g. a downhole safety valve).
It is an aim of the present invention to overcome some of the problems associated with prior art sacrificial breakaway systems by providing a sacrificial breakaway system which allows for a controlled shutdown of well components by disconnecting connectors in a preselected sequence during breakaway.